disconnecting ground (remove third prong) from DAC

[Devnull]

Generally yes. However, a lot of equipment has the audio ground tied to the chassis whether there's a safety ground or not. There may even be multiple connections of the audio ground to chassis, making it very difficult if not impossible to create a safe 'ground lift' facility.

That's why using transformers on the audio outputs is pretty much the only safe way of avoiding ground loops on badly designed equipment.

S.

The safest and easiest way to avoid ground loops is to not buy badly designed equipment.

 

[MRC01]

Disconnecting a safety ground pin is not the same as 'ground lift'.

Over the years I've had a few devices with a "ground lift" switch. The ground "lift" added some impedance to the ground connection, but did not disconnect it. The manual said (A) don't use the switch unless you experience ground loop hum, and (B) if using the switch doesn't affect the hum, set the switch back to normal and troubleshoot to find the root cause.

 

[MRC01]

The safest and easiest way to avoid ground loops is to not buy badly designed equipment.

And don't live in a house having substandard electrical wiring.

 

[sergeauckland]

Over the years I've had a few devices with a "ground lift" switch. The ground "lift" added some impedance to the ground connection, but did not disconnect it. The manual said (A) don't use the switch unless you experience ground loop hum, and (B) if using the switch doesn't affect the hum, set the switch back to normal and troubleshoot to find the root cause.

But the additional impedance is on the audio ground ONLY. The safety ground connection is still directly connected with no additional impedance.

S

 

[Speedskater]

And don't live in a house having substandard electrical wiring.

It's not all that unusual for homes and businesses to have AC wiring errors.
Audio Precision found several when they moved in to their new building.
Those little 3 LED testers only find a few of the errors.

 

[MRC01]

It's not all that unusual for homes and businesses to have AC wiring errors.
Audio Precision found several when they moved in to their new building.
Those little 3 LED testers only find a few of the errors.

I know, that was my point to @Devnull , avoiding ground loops is not as simple as buying well engineered equipment!

 

[KSTR]

Regarding jail, if another party was injured by the removed ground, a civil lawsuit may result but criminal charges are highly unlikely unless it can be proved that the removed ground was an intentional effort to harm someone else or cause damage. That's highly unlikely when the person's goal was to fix a ground loup noise. The injured or damaged party may sue you as a result, but civil lawsuits do not result in jail.

In Germany, this is different. If you knowingly disable the protective earth safety feature on a device and another person gets electrocuted because the device developed a fault (that would have been catched by the safety feature) this is a crime, involuntary manslaughter, and you may be punished with up to 5 years in jail.

EDIT -- by the way, Amazon sold over 5,000 of these in the last month...

"Safety ground disabling" adapters are completely illegal in Germany (and other countries), for obvious reasons.

 

[solderdude]

Over the years I've had a few devices with a "ground lift" switch. The ground "lift" added some impedance to the ground connection, but did not disconnect it. The manual said (A) don't use the switch unless you experience ground loop hum, and (B) if using the switch doesn't affect the hum, set the switch back to normal and troubleshoot to find the root cause.

A real ground lift switch keeps the safety ground connected and only disconnects (or uses a high ohmic resistor + capacitor in parallel) the safety ground to the signal 'ground/common'.
I reckon there are manufacturers that may not do this properly.

 

[unpluggged]

a civil lawsuit may result but criminal charges are highly unlikely unless it can be proved that the removed ground was an intentional effort to harm someone else or cause damage.

Many jurisdictions have provisions for criminal negligence offenses. So tampering with electrical safety measures that would lead to damage, injury, or death, would carry criminal liability.

 

[MRC01]

A real ground lift switch keeps the safety ground connected and only disconnects (or uses a high ohmic resistor + capacitor in parallel) the safety ground to the signal 'ground/common'. ...

Another variation of this is doing it only for 1 channel, either L or R but not both. Years ago I built a ladder stepped passive attenuator (unbalanced) and did this, connecting frame ground to signal ground only on the L channel. I did the same with the phono head amp that I built (based on the DACT CT-100). This measurably reduced noise especially at high (60 dB) gain and helped eliminate ground loops. The first was unpowered so the ground was "frame" but without power. The second was powered by dual 12 V DC batteries, no connection to the wall, but the "frame" ground was connected to the turntable ground.

I never fully understood exactly why it worked. Something about breaking/shorting/preventing a loop circuit around both channels?

 

[mlsstl]

Many jurisdictions have provisions for criminal negligence offenses. So tampering with electrical safety measures that would lead to damage, injury, or death, would carry criminal liability.

I'd like to see an example of someone who faced criminal charges in the U.S. for snipping off the ground prong on a plug for electronics in their home. Does that mean Amazon is going to face criminal charges for selling plug adapters that bypass the ground connection?

 

[chelgrian]

I'd like to see an example of someone who faced criminal charges in the U.S. for snipping off the ground prong on a plug for electronics in their home. Does that mean Amazon is going to face criminal charges for selling plug adapters that bypass the ground connection?

The act of doing such a thing would not be negligence you have to have an effect on someone else which was caused by something you did. There are a lot of civil cases in the US against entities which might have money to pay damages however while there are workable criminal negligence laws on the books in many states they seem to hardly be ever used for electrical safety related incidents.

The US is just weird in many jurisdictions it would be illegal to place such adapters on the market, ‘place on the market’ and the entity which does it is a very specific legal term and it’s probably not the merchant. It usually the manufacturer or importer and both manufacturers and importers can and have been prosecuted for placing unsafe items which do not conform to regulations on the market in various EU jurisdictions.

 

[MaxwellsEq]

I'd like to see an example of someone who faced criminal charges in the U.S. for snipping off the ground prong on a plug for electronics in their home. Does that mean Amazon is going to face criminal charges for selling plug adapters that bypass the ground connection?

Regular reminder: this is forum has an international audience. Many members are not under US jurisdiction. Some are under EU laws, for instance.

 

[Sokel]

Regular reminder: this is forum has an international audience. Many members are not under US jurisdiction. Some are under EU laws, for instance.

Yes.
And on top of that EU already has a portal reporting safety issues, recalls, etc:

Safety Gate: the EU rapid alert system for dangerous non-food products

Safety Gate: the EU rapid alert system for dangerous non-food products allows the 31 participating countries (EU countries, Norway, Iceland and Liechtenstein) and the European Commission to exchange information on products posing a risk to health and safety of consumers and on the measures taken...

ec.europa.eu

 

[sergeauckland]

I'd like to see an example of someone who faced criminal charges in the U.S. for snipping off the ground prong on a plug for electronics in their home. Does that mean Amazon is going to face criminal charges for selling plug adapters that bypass the ground connection?

Assuming those items are sold by Amazon.com, all I can say to that is that the American education system has a lot to answer for if that many people are so ignorant of the dangers. There are benefits to living in Europe where safety seems to be taken more seriously.

S.

 

[KSTR]

Amazon can sell them legally because their intended use is a fixed install *with* protective earth connected to the socket. The problem is this connection is not automatically enforced by the design and thus almost everybody uses these adapters incorrectly, also the correct install is basically never pictured in the product description and photos.

 

[chelgrian]

Amazon can sell them legally because their intended use is a fixed install *with* protective earth connected to the socket. The problem is this connection is not automatically enforced by the design and thus almost everybody uses these adapters incorrectly, also the correct install is basically never pictured in the product description and photos.
View attachment 457133

I was wondering how on earth (yeah I know) such a device could be UL marked…

Laws in the US are somewhat odd most states have laws saying anything that is part of a fixed install must be marked by a Nationally Recognised Testing Laboratory of which UL is the most known but there are others. However as far as I can tell there are few to no laws requiring that appliances must be tested by a NRTL before being placed on the market.

 

[Speedskater]

Most Authority's Having Jurisdiction require that appliances being sold have a UL mark.
True, this rule is seldom enforced, in many jurisdictions.

 

[mhardy6647]

NOTE: I am not recommending hot chassis designs (!)... but... I am always a bit amused by these discussions. Many of you may be too young to remember the millions of "All American Five" AM table radios that were used in virtually all US households for decades. Utterly safe? Heck no. Safe enough in normal application (even with chassis inadvertently "hot" depending on the sense of insertion of the nonpolarized AC plug) -- yeah, pretty much.

Source: https://www.radioworld.com/columns-and-views/remembering-the-allamerican-five
One is most amused by the author's lack of recognition of a schematic from an RCA Receiving Tube manual. RC-25, by the looks of it.
https://www.worldradiohistory.com/B...ooks/RCA-Receiving-Tube-Manual-1967-RC-25.pdf (see page 522)

Note the exceptionally sophisticated power supply design.

The AA5 design gets really interesting when the knobs or cabinet are metal (rare, but not unknown) or they permit the connection of other devices (e.g.., line-in jacks for a 'record player').

I am sure there are still some in (unprotected) use. (most of us who have one... or a few... add a 1:1 AC mains isolation transformer -- at least I hope "we" do!).

 

[Speedskater]

You might tell the families of those that were electrocuted by those death traps, that they were safe.